Due to requirements of low weight and compact design portable working tools are usually run by a crankcase scavenged two-stroke engine. However, a crankcase scavenged four-stroke engine is also conceivable. As a result of the crankcase scavenging the engine is lubricated by oil in the fuel. This means that the tool can be used and managed in different directions during running, i.e. sideways or upside-down. The tools usually have a carburetor connected to an inlet duct, but also a low pressure injection system can be of interest. Since the tool can be used in a lot of positions there is a risk for fuel drops to accumulate inside the inlet duct and then be tipped into the cylinder when the tool's inclination is changed. This can bring about that the engine stops. The greatest risk for this is at lower engine speed. This has also brought about that the carburettor usually is placed near the inlet port, i.e. that the inlet duct is short. Considering engine power at operating speed it would however be preferable to use a longer inlet duct. This could however be associated with said difficulties as well as pure space problems. Therefore the carburetor usually is placed adjacent the cylinder's top section, and provided with some kind of heat protecting baffle. This baffle implies a complication at the same time as temperature problems can still arise for the carburettor. Furthermore, the inlet duct is usually turned obliquely down towards the crankcase. Owing to this the inlet gases can not assist in cooling the critical area around the exhaust port.